As for a system for inspecting a wafer, sheet by sheet, as a substrate having thereon semiconductor devices, there has been known an inspecting system including a plurality of probers as an inspection apparatus and at least one rail guided vehicle (RGV) as a substrate carrier for supplying a wafer to be inspected to each of the probers and then unloading the inspected wafer therefrom.
Each prober includes a prober unit for receiving a wafer and then inspecting a surface thereof and a loader unit for loading a wafer supplied from the RGV into the prober unit and then unloading the inspected wafer therefrom. The loader unit has a box-shaped adaptor unit serving as a temporary storage device for temporarily storing the supplied wafer or the inspected wafer; and a loader transfer arm for transferring the wafer between the adaptor unit and the prober unit. Further, the adaptor unit has a table for mounting thereon the wafer.
The RGV includes a wafer carrier for storing therein a plurality of wafers and an RGV transfer arm for transferring the wafers between the wafer carrier and the adaptor unit of the prober.
The adaptor unit serves as a substrate transfer apparatus for transferring the wafer to the loader transfer arm and the RGV transfer arm. Further, the adaptor unit is configured such that the table does not interfere with each of the transfer arms in moving directions of the loader transfer arm and the RGV transfer arm. In other words, a moving path of each transfer arm is provided in the adaptor unit.
For example, in the adaptor unit 100 illustrated in FIG. 10, the table is formed by four supporting members 101 protruded from corner portions of the adaptor unit 100. Since the supporting members are spaced from each other, the approach path of each transfer arm, e.g., the loader transfer arm 102, is allowed (see, e.g., Japanese Patent Laid-open Publication NO. H6-163667). In such adaptor unit 100, the four supporting members 101 support a peripheral portion of the wafer W at four locations.
Meanwhile, if the wafer mounted on the table of the adaptor unit is severely misaligned, the wafer is not loadable into the prober unit. Accordingly, there has been developed an adaptor unit and a method for correcting the misalignment of a wafer.
As for an adaptor unit for correcting the misalignment of a wafer, there is known an adaptor unit 110 having a centering device shown in FIG. 11. The adaptor unit 110 includes a wafer support 111 for mounting thereon the wafer W loaded by the RGV transfer arm; a pair of centering plates 112 disposed at both sides of the wafer support 111 so as to surround the mounted wafer W; and an extending and contracting mechanism for extending and contracting the centering plate 112. In such adaptor unit 110, when a gap between the pair of centering plates 112 is shortened, the centering plates 112 are contacted with a peripheral surface of the wafer W mounted on the wafer support 111, thereby centering the wafer W (see, e.g., Japanese Patent Laid-open Publication NO. 2003-224177).
Further, in the adaptor unit 110, the centered wafer W is accommodated in a wafer chamber 113 provided at a lower portion of the adaptor unit 110. Provided in the wafer chamber 113 are supporting members 114a and 114b for supporting the peripheral portion of the wafer W at two locations. The supporting members 114a and 114b serve as a table of the wafer W.
As for a method for correcting the misalignment of the wafer, there is known a method for contacting the wafer W mounted on the RGV transfer arm 121 with a wall of the carrier 120 for accommodating therein the wafer W, as described in FIG. 12. To be specific, the wafer W is mounted on the RGV transfer arm 121 without being adsorbed and, then, the RGV transfer arm 121 moves into the carrier 120. Next, the peripheral portion of the wafer W is contacted with an inner wall of the carrier 120. In such state, the RGV transfer arm 121 is extended. At this time, a relative position of the wafer W with respect to the RGV transfer arm 121 changes. When the RGV transfer arm 121 is extended to a specific position, the wafer W is adsorbed by the RGV transfer arm 121 (see, e.g., Japanese Patent Laid-open Publication No. 2002-203890).
By properly setting the relative position of the RGV transfer arm 121 with respect to the carrier 120, it is possible to adjust the relative position of the RGV transfer arm 121 with respect to the wafer W and further to center the wafer W. The peripheral portion of the centered wafer W is supported at two locations by the supporting members 122a and 122b protruded from the inner wall of the carrier 120, wherein the supporting members 122a and 122b face each other with the wafer W therebetween.
However, in the aforementioned adaptor units or carriers, a plurality of supporting members support at least two locations of the peripheral portion of the wafer W. Thus, if heights of supporting members are different, the wafer W becomes inclined, which inhibits a proper transfer of the wafer W. An inclination of the wafer W may cause a second misalignment of the wafer W.
Moreover, in the aforementioned adaptor units or carriers, since plurality of supporting members support at least two locations of the peripheral portion of the wafer W, only a single sized wafer W can be supported and, thus, wafers W of various sizes cannot be supported and properly transferred.